The Symbionts

As the epochs passed, the two species molded one another to form a well-integrated union. The little arachnoid, no bigger than a chimpanzee, rode in a snug hollow behind the great "fish's" skull, his back being stream-lined with the contours of the larger creature. The tentacles of the ichthyoid were specialized for large-scale manipulation, those of the arachnoid for minute work. A biochemical interdependence also evolved. Through a membrane in the ichthyoid's pouch an exchange of endocrine ...